1. Field of the Invention
The present invention relates to a tool system and method for cleaning out restrictions located substantially downhole in oil wells and the like, and more particularly to a tool system for cleaning out the zone below a packer without the need for removing the packer, utilizing a tool which has a relatively small diameter, less than the diameter of the production tubing, but having radically extendable cleaning blades which are expanded out after the tool is longitudinally moved through the production tubing and located down below the packer. The zone below the packer to be cleaned out is filled with debris restricting flow from the zone to the interior of the production tubing, and the tool system of the invention in its expanded configuration rotated about its longitudinal axis, moving the blade within the zone to loosen the debris, which is then removed by fluid circulation. Additionally, the present invention relates to such a tool having a replaceable blade set allowing for the same tool to be used for different diameter casings.
2. Prior Art and General Background
Following drilling operations for an oil or gas well, a string of steel casing is installed into the well bore to isolate the producing interval or zone from other formations. A string of steel production tubing is installed longitudinally inside the casing with a packer set above the production perforations, and the well is produced through the production tubing. Often times a sand screen is set opposite the production perforations to restrict entry of sand grains from unconsolidated sandstone formations into the casing and tubing. In the event this precautionary measure is inadequate, or for other reasons, which may exist over a period of time, such as scale, corrosion, etc., flow from the well may become restricted or cease, requiring clean-out of the debris in the zone below the packer.
The usual procedure to resolve this problem has been to employ a workover rig, kill the well with weighted drilling fluids, retrieve the tubing and packer, and clean out the restriction or debris. This operation is considerably expensive, especially when the tubing and packer cannot be easily retrieved.
In general it would not be suitable to use apparatus for severing well casing such as described in Smith, U.S. Pat. No. 3,378,072 issued on Apr. 16, 1968, as the apparatus was not intended to be made in a size small enough to be lowered through the interior of a production tubing string, which is generally in the neighborhood of 2 1/2-4 1/2 inches, and the apparatus would, in any event, sever the casing and would not be suitable for movement of the blade longitudinally along the axis of the casing while the blade is rotated. For other examples of apparatus for severing well casing, see for example U.S. Pat. Nos. 4,068,711 (issued Jan. 17, 1978 to Aulenbacher); 2,328,782 (issued Sept. 7, 1943 to P. T. Bynum); 2,284,211 (issued May 26, 1942 to G. E. Justice); and RE 21,824 (issued June 10, 1941 to G. A. Lowrey).